Pam Ldap (debian) problem

Hi,

i dont get postgres working with pam to use an external ldap server to authenticate users.
i think the problems is that postgres is using the wrong pam file,
namely he uses pam_unix where he should use pam_ldap.so.

postgres version 7.3.2
debian version 3 (kernel 2.4)

any help is much appreciated

ive included the following files:
/etc/hosts
/etc/pam.conf
/etc/pam_ldap.conf
/etc/pam.d/postgresql
/etc/postgresql/pg_hba.conf
/etc/postgresql/postgresql.conf
/etc/postgresql/postmaster.conf
/var/log/messages
/var/log/postgres.log (is empty)
/var/log/auth.log

in short the logs:

Sep 11 12:48:49 damian postgres[1892]: [1] LOG: connection received: host=10.18.10.47 port=32882
Sep 11 12:48:53 damian postgres[1893]: [1] LOG: connection received: host=10.18.10.47 port=32883

and

Sep 11 12:48:49 damian PAM_unix[1892]: auth could not identify password for [wibrt]
Sep 11 12:48:49 damian 18.10.47 authentication[1892]: [2] LOG: CheckPAMAuth: pam_authenticate failed: 'Conversation error'
Sep 11 12:48:49 damian 18.10.47 authentication[1892]: [3] FATAL: PAM authentication failed for user "wibrt"
Sep 11 12:48:53 damian PAM_unix[1893]: authentication failure; (uid=31) -> wibrt for sameuser service
Sep 11 12:48:55 damian 18.10.47 authentication[1893]: [2] LOG: CheckPAMAuth: pam_authenticate failed: 'Authentication failure'
Sep 11 12:48:55 damian 18.10.47 authentication[1893]: [3] FATAL: PAM authentication failed for user "wibrt"

tnx,
Wim